Electrical synapses between neurons are formed by gap junction channels, through which ions and metabolites pass directly from one cell to the next. Recent evidence indicates that other proteins are associated with connexins at gap junctions, and we have termed this macromolecular complex the Nexus. We hypothesize that the Nexus components may regulate both the properties of the gap junction channels and also may function in intracellular signal transduction. A new gap junction protein, connexin36, has been identified that is largely restricted in its expression to neurons, and we have shown that the channels formed by this connexin have properties that seem to uniquely suit it as a neuronal connexin. The goals of this grant application are to characterize the gating, permeability and conductance properties with regard to the protein domains involved, to identify other proteins in brain and neuron lysates that bind to connexin36, measure the strengths of interaction using surface plasmon resonance, and perform physiological experiments on neuron-like cells to determine the effects of Cx36 expression on neuronal differentiation and gene expression patterns. In addition, a major goal of this application is to obtain structural information using spectroscopic methods regarding domains of Cx36 that interact with each other and with other proteins. These studies use a multidisciplinary approach directed at exploring a new concept in the field and as such are expected to lead to novel understanding of regulation and roles of gap junctions in the nervous system.